Time-varying image decoding display device and time-varying image decoding display method

ABSTRACT

In a moving picture decoding display apparatus and moving picture decoding display method according to the present invention, moving picture decoder  101  decodes a moving picture signal, RGB matrix manipulation section  103  converts the decoded video signal in YCbCr format into a video signal in RGB format, contrast/brightness adjusting section  104  adjusts the contrast and brightness of the video signal in RGB format, and liquid crystal display module section  110  displays the adjusted video signal on liquid crystal panel  109.  At this point, operation control section  105  switches on and off the operation of RGB matrix manipulation section  103  and contrast/brightness adjusting section  104  corresponding to the actual frame rate in moving picture decoder  101,  and only when the operation is “on”, the section  105  controls so that the video signal from contrast/brightness adjusting section  104  is stored in video RAM  107  in liquid crystal display module section  110.  Thus, since the operation of required video signal processing is switched on and off based on the actual frame rate, it is possible to suppress the power consumption in the entire apparatus.

TECHNICAL FIELD

[0001] The present invention relates to a moving picture decodingdisplay apparatus and moving picture decoding display method which areinstalled onto a mobile station apparatus such as a cellular telephoneor an information communication terminal apparatus provided withfunctions of communications and computer in a mobile communicationsystem, and which convert video signals including brightness signal Yand color-difference signals Cb and Cr from a moving picture decoderinto video signals in primary-color signal format composed of R (Red), G(Green) and B (Blue) to display moving pictures.

BACKGROUND ART

[0002] In battery-powered portable terminal apparatuses, liquid crystaldisplay apparatuses have been proposed which reduce power consumption.An example is disclosed in Japanese Laid-Open Patent PublicationHEI5-53541 in which the access to a video memory is monitored for apredetermined time to control a driving section of a display apparatus,or in Japanese Laid-Open Patent Publication HEI9-212134 in which updatedpart of display data is only transferred to a display memory. Aconventional moving picture decoding display apparatus that is a liquidcrystal display apparatus will be described with reference to FIG. 1.

[0003]FIG. 1 is a block diagram illustrating a configuration of aconventional moving picture decoding display apparatus. Generally,moving picture coding/decoding schemes such as ITU-T H.263 and MPEG useimage formats such as CIF (Common Intermediate Format) and QCIF (QuarterCIF). Herein, as an example, a case is explained that the image formatis of CIF4:2:2 (Valid display area: 352 pixels×288 scanning lines).

[0004] Moving picture decoding display apparatus 50 illustrated in FIG.1 is provided with moving picture decoder 51, video signal converter 52having delay line section 53 and RGB matrix manipulation section 54, andliquid crystal display module section 55 having video RAM 56,contrast/brightness adjuster 57, driving signal converter 58 and liquidcrystal panel 59.

[0005] Moving picture decoder 51 outputs video signals in YCbCr format.The video signal in YCbCr format includes brightness signal Y,color-difference signal C on which time-division multiplexed are twocolor-difference signals (Cb and Cr), vertical sync signal VDN,horizontal sync signal HDN, and clock signal VCK used in transferringvideo data.

[0006] Video signal converter 52 has RGB matrix manipulation section 54that converts video signals in YCbCr format into LCD_R, LCD_G and LCD_Bin RGB format using brightness signal Y and color-difference signal C,and delay line section 53 that adds a delay equivalent to RGB matrixmanipulation section 54 to vertical sync signal VDN and horizontal syncsignal HDN output from moving picture decoder 51, and outputs verticalsync signal VSYNCN and horizontal sync signal HSYNCN to liquid crystaldisplay module section 55.

[0007] Liquid crystal display module section 55 has video RAM 56 thattemporarily stores a video signal in RGB format output from video signalconverter 52, contrast/brightness adjuster 57 that adjusts a dynamicrange and offset amount of the video signal in RGB format read fromvideo RAM 56, driving signal converter 58 that generates a drivingsignal for driving liquid crystal panel 59 from vertical sync signalVSYNCN and horizontal sync signal HSYNCN output from video signalconverter 52 and R′G′B′ signal output from contrast/brightness adjuster57, and liquid crystal panel 59 that displays moving picturescorresponding to the driving signal.

[0008] The operation of moving picture decoding display apparatus 50with the above configuration will be described with reference to FIGS. 2to 4. FIG. 2 is a timing diagram of input and output signals in thevideo signal converter in the conventional moving picture decodingdisplay apparatus, FIG. 3 shows graphs illustrating input/outputcharacteristics to explain the processing in the contrast/brightnessadjuster, and FIG. 4 is a diagram illustrating moving pictures to bedisplayed on the liquid crystal panel.

[0009] Moving picture decoder 51 outputs to video signal converter 52,as shown in FIG. 2, as moving-picture video signals, vertical syncsignal VDN, horizontal sync signal HDN, brightness signal Y (8 bits) andcolor-difference signal C (8 bits) with time-division multiplexed twocolor-difference signals (Cb and Cr), in synchronization with a fallingedge of clock signal VCK.

[0010] Moving picture decoder 51 inputs brightness signal Y andcolor-difference signal C to RGB matrix manipulation section 54. In thevideo signal in CIF4:2:2 format, as shown in FIG. 2, twocolor-difference components, i.e., Cb and Cr are time-divided. Acolor-difference component of an odd-numbered pixel number isinterpolated by a color difference of an even-numbered pixel number,converted into the signal in RGB format, and output as signal LCD_R,LCD_G and LCD_B. Specifically, the section 54 calculates as describedbelow.

LCD _(—) R=Y+1.402*Cr

LCD _(—) G=Y−0.344*Cb−0.714×Cr

LCD _(—) B=Y+1.772*Cb

[0011] Herein, it is assumed that each has 6 bits.

[0012] Meanwhile, moving picture decoder 51 inputs vertical sync signalVDN and horizontal sync signal HDN to delay line section 53. Delay linesection 53 adds a processing delay of RGB matrix manipulation section 54to the input signals, and outputs vertical sync signal VSYNCN andhorizontal sync signal HSYNCN to liquid crystal display module section55.

[0013] Liquid crystal display module section 55 temporarily storesprovided video signals LCD_R, LCD_G and LCD_B in video RAM 56 everyrising edge of VCK. Video RAM 56 reads out the signals as R, G and B tooutput to contrast/brightness adjuster 57.

[0014] The input/output characteristics that are functions ofcontrast/brightness adjuster 57 are expressed byY=Contrast(X−32)+32+Brightness where an input is X and an output is y,as shown in FIG. 3. These signals are processed for each of R, G and B.When an output range is of 6 bits, since the range is from 0 to 63, theoutput Y exceeding the range undergoes clipping to be in the range of 0to 63.

[0015] These characteristics can be changed with values of contrast andbrightness given from the outside as parameters. The processed outputsignals R′, G′ and B′ are provided to driving signal converter 58 alongwith vertical sync signal VSYCN and horizontal sync signal HSYNCN, andthe section 58 generates a signal for driving liquid crystal panel 59 todisplay moving pictures.

[0016] It is generally known that liquid crystal panel 59 should drivevideo signals in about 60 Hz so as to suppress the flicker of displayedimage. In other words, image display intervals in FIG. 4 need to beone-sixtieth seconds. In conventional moving picture decoding displayapparatus 50 as described above, the video signal is output from movingpicture decoder 51 at 60 Hz, and the processing in video signalconverter 52 and subsequent sections is executed at 60 Hz consistently.

[0017] However, in the conventional apparatus, there are problems asdescribed later. That is, the decoding processing in moving picturedecoder 51 is dependent on its performance and handling image size,decoded image quality, coding bit rate, etc., and decoded images are notalways different every 60 Hz. In other words, although images are outputat a frame rate of 60 fps, some sheets of same image are providedactually. As shown in FIG. 4, image frames with the same contents, forexample, three sheets of image A and two sheets of image C, are present.The actual frame rate in portable video telephones is estimated atapproximately 15 fps. The processing at 60 Hz is required for readingdata from video RAM 56 and thereafter, and the processing at 60 Hz invideo signal converter 52 disposed before video RAM 56 results incurrent dissipation.

[0018] Further, contrast/brightness adjuster 57 disposed after video RAM56 also executes processing at 60 Hz always, resulting in disadvantagesin current consumption.

DISCLOSURE OF INVENTION

[0019] It is an object of the present invention to provide a movingpicture decoding display apparatus and moving picture decoding displaymethod that switch on and off the operation of required video signalprocessing based on an actual frame rate, and thereby are capable ofsuppressing power consumption in the entire apparatus.

[0020] The object is achieved by displaying moving pictures using videosignals subjected to RGB format conversion and contrast/brightnessadjustment when the video contents change, while displaying videos usingvideo signals stored in a video RAM which are not subjected to the RGBformat conversion and contrast/brightness adjustment when the videocontents do not change.

BRIEF DESCRIPTION OF DRAWINGS

[0021]FIG. 1 is a block diagram illustrating a configuration of aconventional moving picture decoding display apparatus;

[0022]FIG. 2 is a timing diagram of input and output signals in a videosignal converter in the conventional moving picture decoding displayapparatus;

[0023]FIG. 3A shows a graph illustrating input/output characteristics toexplain the processing in a contrast/brightness adjuster in theconventional moving picture decoding display apparatus;

[0024]FIG. 3B shows another graph illustrating input/outputcharacteristics to explain the processing in the contrast/brightnessadjuster in the conventional moving picture decoding display apparatus;

[0025]FIG. 4 is a diagram illustrating moving pictures to be displayedon a liquid crystal panel in the conventional moving picture decodingdisplay apparatus;

[0026]FIG. 5 is a block diagram illustrating a configuration of a movingpicture decoding display apparatus according to a first embodiment ofthe present invention;

[0027]FIG. 6 is a timing diagram of input and output signals in a videosignal converter in the moving picture decoding display apparatusaccording to the first embodiment;

[0028]FIG. 7 is a diagram illustrating moving pictures output from amoving picture decoder to be displayed on a liquid crystal panel in themoving picture decoding display apparatus according to the firstembodiment;

[0029]FIG. 8 is a block diagram illustrating a configuration of a movingpicture decoding display apparatus according to a second embodiment ofthe present invention; and

[0030]FIG. 9 is a diagram illustrating moving pictures output from amoving picture decoder to be displayed on a liquid crystal panel in themoving picture decoding display apparatus according to the secondembodiment.

BEST MODE FOR CARRYING OUT THE INVENTION

[0031] Embodiments of the present invention will be described below withreference to accompanying drawings.

[0032] (First Embodiment)

[0033]FIG. 5 is a block diagram illustrating a configuration of a movingpicture decoding display apparatus according to a first embodiment ofthe present invention.

[0034] Moving picture decoding display apparatus 100 illustrated in FIG.5 is provided with moving picture decoder 101, video signal converter106 having delay line section 102, RGB matrix manipulation section 103,contrast/brightness adjusting section 104, and operation control section105, and liquid crystal display module section 110 having video RAM 107,driving signal converter 108 and liquid crystal panel 109.

[0035] Moving picture decoder 101 outputs to video signal converter 106a video signal for displaying moving pictures in YCbCr format composedof brightness signal Y and color-difference signal C on whichtime-division multiplexed are two color-difference signals (Cb and Cr),vertical sync signal VDN, horizontal sync signal HDN, video signaltransfer clock signal VCK, and VFLG indicating that a video signal isupdated from a last frame.

[0036] RGB matrix manipulation section 103 converts the video signal inYCbCr format into a video signal in RGB format.

[0037] Contrast/brightness adjusting section 104 adjusts the contrastand brightness of each input signal in RGB format.

[0038] Operation control section 105 receives video signal update signalVHLG from moving picture decoder 101, switches on or off the operationof RGB matrix manipulation section 103 and contrast/brightness adjustingsection 104, and outputs video update signal VALID to liquid crystaldisplay module section 110.

[0039] Delay line section 102 adds a processing delay of RGB matrixmanipulation section 103 and contrast/brightness adjusting section 104to vertical sync signal VDN and horizontal sync signal HDN from movingpicture decoder 101, and outputs vertical sync signal VSYNCN andhorizontal sync signal HSYNCN to liquid crystal display module section110.

[0040] Video RAM 107 temporarily stores video signals LCD_R, LCD_G andLCD_B in RGB format output from video signal converter 106.

[0041] Driving signal converter 108 generates a driving signal for theliquid crystal panel from videos signals R′, G′ and B′ in RGB formatread from vide RAM 107, and vertical sync signal VSYNCN and horizontalsync signal HSYNCN output from video signal converter 106.

[0042] Liquid crystal panel 109 displays moving pictures correspondingto the driving signal.

[0043] The operation of moving picture decoding display apparatus 100with the above configuration will be described with reference to FIGS. 6and 7. FIG. 6 is a timing diagram of input and output signals in videosignal converter 106, and FIG. 7 is a diagram illustrating movingpictures output from moving picture decoder 101 to be displayed onliquid crystal panel 109.

[0044] Moving picture decoder 101 outputs to video signal converter 106,as shown in FIG. 6, vertical sync signal VDN, horizontal sync signalHDN, brightness signal Y (8 bits) of decoded moving picture,color-difference signal C (8 bits) with time-division multiplexed twocolor-difference components (Cb and Cr), and a signal VFLG indicative ofoutputting an image different from that of a last frame, insynchronization with a falling edge of clock signal VCK. In addition,VFLG (frame Valid FLaG) is generated to indicate that memory contentshave been updated when image data is written in a frame memory of themoving picture decoder or the contents are read out.

[0045] In this example, signal VFLG of 1 indicates that a current movingpicture is different from that of a last frame, while the signal of 0indicates that a current moving picture is the same as that of a lastframe. In video signal converter 106, corresponding to logic 0/1 ofsignal VFLG, operation control section 105 generates a control signalfor controlling ON and OFF of the operation of RGB matrix manipulationsection 103 and contrast/brightness adjusting section 104, and signalVALID for notifying that the contents of an image has been changed toliquid crystal display module section 110.

[0046] The section 105 switches on the operation of RGB matrixmanipulation section 103 and contrast/brightness adjusting section 104when signal VFLG is 1, while switching off the operation when signalVFLG is 0.

[0047] Corresponding to the control signal from operation controlsection 105, when the operation is switched on, RGB matrix manipulationsection 103 generates video signals R, G and B in RGB format frombrightness signal Y and color-difference signal C. Specifically, thesection 103 calculates as described below, and may be composed of amultiplier and adder, or a ROM storing a conversion table.

R=Y+1.402×Cr

G=Y−0.344×Cb−0.714×Cr

B=Y+1.772×Cr

[0048] When the operation of the section 103 is switched off, the supplyof operation clock is stopped and so on, thereby reducing powerconsumption. Corresponding to the control signal from operation controlsection 105, when the operation is switched on, contrast/brightnessadjusting section 104 executes the processing based on followingequations.

LCD _(—) R=Contrast*(R−32)+Brightness+32

LCD _(—) G=Contrast*(G−32)+Brightness+32

LCD _(—) B=Contrast*(B−32)+Brightness+32

[0049] The contrast and brightness is provided from the outside asparameters. These parameter values are sometimes provided for each of R,G and B independently. When the operation is switched off, the section104 outputs “black” (all bits are 0) and stops outputting.

[0050] Moving picture decoder 101 inputs vertical sync signal VDN andhorizontal sync signal HDN to delay line section 102. Delay line section102 adds a processing delay of RGB matrix manipulation section 103 andcontrast/brightness adjusting section 104 to the input signals, andoutputs vertical sync signal VSYNCN and horizontal sync signal HSYNCN toliquid crystal display module section 110.

[0051] Liquid crystal display module section 110 temporarily storesprovided video signals LCD_R, LCD_G and LCD_B in video RAM 107 everyrising edge of VCK only when signal VALID is 1, while not storing thesignals in video RAM 107 when signal VALID is 0. Signals LCD_R, LCD_Gand LCD_B stored in video RAM 107 are read out as signals R′, G′ and B′always at 60 fps and is output to driving signal converter 108.

[0052] Driving signal converter 108 generates a driving signal fordriving liquid crystal panel 109 from vertical sync signal VSYNCN,horizontal sync signal HSYNCN and signals R′, G′, and B∝0, so thatmoving pictures are displayed on liquid crystal panel 109.

[0053]FIG. 7 shows moving pictures output from moving picture decoder101 to be displayed on liquid crystal panel 109 in the abovedescription. Brightness signal Y and color-difference signal C outputfrom moving picture decoder 101 are dependent on its performance andhandling image size, decoded image quality, coding bit rate, etc., anddecoded pictures are not always different every 60 Hz.

[0054] As an example in FIG. 7, image frames with the same contents, forexample, three sheets of image A, one sheet of image B and two sheets ofimage B, are continued. Using signal VFLG, video signal converter 106outputs video signals LCD_R, LCD_G and LCD_B only when the contents ofan image are changed. Video signals R′, G′ and B′ actually indicated onliquid crystal panel 109 are displayed in the same way as in the videosignals provided from moving picture decoder 101.

[0055] Thus, according to moving picture decoding display apparatus 100of this embodiment, in accordance with the substantial frame rate, onlywhen the image contents are changed, RGB format conversion andcontrast/brightness adjustment is executed, and it is thereby possibleto reduce power consumption in RGB matrix manipulation section 103 andcontrast/brightness adjusting section 104.

[0056] (Second Embodiment)

[0057]FIG. 8 is a block diagram illustrating a configuration of a movingpicture decoding display apparatus according to the second embodiment ofthe present invention. In addition, in the second embodiment illustratedin FIG. 8, sections similar to those in FIG. 5 are assigned the samereference numerals to omit descriptions thereof.

[0058] Moving picture decoding display apparatus 200 illustrated in FIG.8 is different from moving picture decoding display apparatus 100illustrated in FIG. 5 in respects that video signal converter 106 hascompulsory screen update detector 401, and operation control section 105performs the control operation as described below.

[0059] The parameter value provided to contrast/brightness adjustingsection 104 from the outside is also input to compulsory screen updatedetector 401. Compulsory screen update detector 401 determines whetheror not the parameter value has been updated from an already set value.For example, the section 401 outputs “1” when the value is update, whileoutputting “0” when the value is not update, to operation controlsection 105.

[0060] When signal VFLG from moving picture decoder 101 is “1”indicating that the moving picture is updated, or the signal fromcompulsory screen update detector 401 is “1” indicating that theparameter value is updated, operation control section 105 switches onthe operation of RGB matrix manipulation section 103 andcontrast/brightness adjusting section 104, and sets signal VALID at “1”to notify that the image contents are changed to liquid crystal displaymodule section 110. When signal VFLG is “O” and the signal indicatingwhether the parameter value is updated is “0”, the section 105 switchesoff the operation of RGB matrix manipulation section 103 andcontrast/brightness adjusting section 104, and sets signal VALID at “0”.

[0061]FIG. 9 is a diagram illustrating moving pictures output frommoving picture decoder 101 to be displayed on liquid crystal panel 109.Even when the moving picture output from moving picture decoder 101 isstopped in Q, once the parameter value is updated as described above,with the updated value reflected, image Q′ subjected to the processingin contrast/brightness section 104 is displayed on liquid crystal panel109.

[0062] Thus, according to moving picture decoding display apparatus 200of the second embodiment, in accordance with the substantial frame rate,when the image contents are changed, RGB format conversion andcontrast/brightness adjustment is executed, and it is thereby possibleto reduce power consumption in RGB matrix manipulation section 103 andcontrast/brightness adjusting section 104.

[0063] Further, when the parameter value for contrast/brightnessadjusting section 104 is changed, it is possible to immediately displaythe picture in which the change is reflected.

[0064] As described above, according to the present invention, theoperation of required video signal processing is switched on or offbased on an actual frame rate, and it is thereby possible to suppressthe power consumption in the entire apparatus.

[0065] This application is based on the Japanese Patent Application No.2001-067308 filed on Mar. 9, 2001, entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

[0066] The present invention is suitable for use in a moving picturedecoding display apparatus and moving picture decoding display methodwhich are installed onto a mobile station apparatus such as a cellulartelephone or an information communication terminal apparatus providedwith functions of communications and computer in a mobile communicationsystem, and which convert video signals including brightness signal Yand color-difference signals Cb and Cr from a moving picture decoderinto video signals in primary-color signal format composed of R (Red), G(Green) and B (Blue) to display moving pictures.

1. A moving picture decoding display apparatus comprising: a decodingsection that decodes a moving picture signal; a converting section thatconverts a decoded video signal in YCbCr format into a video signal inRGB format; an adjusting section that adjusts contrast and brightness ofthe video signal in RGB format; a control section that operates theconverting section and the adjusting section corresponding to an actualframe rate in the decoding section; and a display section that displaysthe video signal adjusted in the adjusting section.
 2. The movingpicture decoding display apparatus according to claim 1, furthercomprising: a detecting section that detects a change in parameter valueinput to the adjusting section from the outside to adjust the contrastand brightness, wherein corresponding to detection of the change inparameter value in the detecting section, the control section switcheson and off operation of the converting section and the adjustingsection.
 3. The moving picture decoding display apparatus according toclaim 1, wherein the display section has a memory section for storing avideo signal, and only when the operation of the converting section andthe adjusting section is switched on, the control section controls sothat the video signal from the adjusting section is stored in the memorysection.
 4. A mobile station apparatus comprising the moving picturedecoding display apparatus according to claim
 1. 5. A moving picturedecoding display method comprising: decoding a moving picture signal;converting a decoded video signal in YCbCr format into a video signal inRGB format; adjusting contrast and brightness of the converted videosignal; displaying the adjusted video signal; and controlling convertingoperation and adjusting operation corresponding to an actual frame ratein decoding.
 6. The moving picture decoding display method according toclaim 5, wherein in adjusting the contrast and brightness, a change inparameter value provided from the outside for adjustment is detected,and corresponding to detection of the change in parameter value, theconverting operation and the adjusting operation is controlled.
 7. Themoving picture decoding display method according to claim 5, whereinonly when the converting operation and the adjusting operation isswitched on, the video signal is temporarily stored, which is performedin displaying the video signal.